Front vacuum disconnect vs. NP242

[MJR]

Actually, way back in the dreamtime, when such vehicles as a Jeep CJ-5 came without locking hubs, that's one of the main reasons people did install Warn hubs - that and drivetrain wear. But of course, the hub conversion truly disconnects all of the drivetrain, whereas the axle disconnect leaves 1 and a half axle shafts turning, plus a part of the differential innards, a much lesser saving.

I was under the impression that flat-towing an XJ requires that the front axle be connected. The procedure for the 87 was pretty specific, requiring that the TC be shifted into N while the engine ran, so that the disco would engage.

There is a difference between doing it for towing ease (turns) and just fuel economy though.

Correct me if I am wrong but in 2wd the front axle disconnect is already disengaged.

It is Jeep's recommendation that 4wd Jeeps be towed on a flat bed trailer or sling type using tow dollies provided all wheels are lifted off the ground. Now with that said there are people that regularly flat tow their Jeeps.

 

[1986xj]

I thought the 242's and other fultime cases came with non disco axles because of there being a coupler in the tcase for the fulltime 4wd. I know the 208 and 209 tcase equipped Jeeps would just roll away (according to the owners maual) when in park when in FT if you would put lock out hubs on the front and didn't have them "locked", a disengaged disco axle would be the same I would think... Is the coupler in the 242 the same, for it to work correctley on dry pavement I would think it would have to be.
Mike B.

 

[MJR]

Yes the Jeeps with a 242 came with a non disconnect axle. The 242 has a open differential for Full Time mode.

 

[Matthew Currie]

There is a difference between doing it for towing ease (turns) and just fuel economy though.

Correct me if I am wrong but in 2wd the front axle disconnect is already disengaged.

It is Jeep's recommendation that 4wd Jeeps be towed on a flat bed trailer or sling type using tow dollies provided all wheels are lifted off the ground. Now with that said there are people that regularly flat tow their Jeeps.

There's a difference between "towing" and "flat towing." The owner's manual for my 87 had a specific procedure for flat-towing, which, as I recall, involved turning the engine on, then putting the TC in neutral. It was stressed that this must be done with the engine on to ensure that the front axle is engaged so that both driveshafts turn, to avoid starving the bearings in the TC.

 

[MJR]

There's a difference between "towing" and "flat towing." The owner's manual for my 87 had a specific procedure for flat-towing, which, as I recall, involved turning the engine on, then putting the TC in neutral. It was stressed that this must be done with the engine on to ensure that the front axle is engaged so that both driveshafts turn, to avoid starving the bearings in the TC.

Well I fail to see how the bearings in a 231 or 242 would starve for oil when the oil pump is driven by the rear output but you are correct it that is what the owners manuals said.

I wonder if the front and rear outputs are locked together in neutral while the input is disengaged. I'll have to check it when I get a chance. Otherwise it would rely on splash lubrication from the front output if the rear was off the ground.

 

[Fast95Neon]

can i see pics with a disco and non disco axle and t case?

 

[cherokee chuck]

My son has a 95 with a 231 & AX-15 & we put a 91 disco 30 with a posi-loc just so he can run a locker. It works just like it should. Shift on the fly is a relative term. You can engage the axle at 25 or 30 mph if you finess it. but its like shifting a NP205 on the fly, or a clutchless shift with a manual trans. I think disco D30s. unfairly get a bad rap. Most late model four wheel drives use a disconect axle, all YJs came with them. Chrysler discontinued them in the XJ for cost reasons not because they don't work. It's a cheap alternative to locking hubs if you are running 33"s or smaller. Just my opinion for what it's worth.:soapbox: And I don't run one in my 87 with a 242 btw.

 

[Fast95Neon]

i have a 91 with a non disco axle....
but a bought a 242 cuz my current 242 had a crack in it....but the case i bought has a sensor in the front on the top next to the vacuum line...my old one doesent have that....does it need to be connceted or will i be ok?